Study: Chemicals in some vegetables prevent cancer in mice

A study found chemicals in some vegetables, including broccoli, helped prevent colon cancer in mice. Photo by Engin_Akyurt/pixabay

Aug. 15 (UPI) -- Chemicals in some vegetables, including kale, cabbage and broccoli, helped prevent colon cancer in mice, according to a study.

Researchers at Francis Crick Institute in England found mice fed on a diet rich in indole-3-carbinol were protected from gut inflammation and colon cancer. The findings were published Tuesday in the journal Immunity.

Indole-3-carbinol is produced when vegetables from the Brassica genus are digested.

"This study in mice suggests that it's not just the fiber contained in vegetables like broccoli and cabbage that help reduce the risk of bowel cancer, but also molecules found in these vegetables too,"
Dr. Tim Key, Cancer Research UK's expert on diet and cancer, said in a Crick press release. "This adds to the evidence that a healthy diet, rich in vegetables, is important."

Although health benefits of vegetables have been determined, this is the first study that found how I3C in the diet can prevent colon inflammation and cancer by activating a protein called the aryl hydrocarbon receptor, or AhR.

"Seeing the profound effect of diet on gut inflammation and colon cancer was very striking," senior author Dr. Gitta Stockinger, group leader at the Francis Crick Institute, said. "We often think of colon cancer as a disease promoted by a Western diet rich in fat and poor in vegetable content, and our results suggest a mechanism behind this observation."

They found that these AhR-promoting chemicals can correct defects caused by insufficient AhR stimulation. They offer resistance to intestinal infections and prevent colon cancer by passing signals to immune cells and epithelial cells in the gut lining, the researchers found.

"We studied genetically modified mice that cannot produce or activate AhR in their guts, and found that they readily developed gut inflammation which progressed to colon cancer," first author Dr. Amina Metidji from the Francis Crick Institute said. "However, when we fed them a diet enriched with I3C, they did not develop inflammation or cancer."

They also found that when mice already were developing cancer, switching to the I3C-enriched diet had significantly fewer tumors, which were also more benign.

Without Ahr's repair capabilities, the cells divide uncontrollably, possibly leading to colon cancer.

"These findings are a cause for optimism; while we can't change the genetic factors that increase our risk of cancer, we can probably mitigate these risks by adopting an appropriate diet with plenty of vegetables," Stockinger said.

They also found normal mice fed on standard or I3C-enriched food did not develop tumors during the study, but those fed on a "purified control diet" did. The diet fulfilled the animal's nutritional needs but is free of allergens, pathogens or variable ingredients.

"Normal mice on the purified control diet developed colon tumors within 10 weeks, whereas mice on the standard chow didn't develop any," co-corresponding author Dr. Chris Schiering, who worked on the study at the Crick and now works at Imperial College London, said. "This suggests that even without genetic risk factors, a diet devoid of vegetable matter can lead to colon cancer."

The researchers want to conduct experiments in organoids made from human gut biopsies and eventually human trials.

"A number of epidemiological studies suggested that vegetables may be protective against cancer," Stockinger said. "However, there is very little literature on which vegetables are the most beneficial or why. Now that we've demonstrated the mechanistic basis for this in mice, we're going to investigate these effects in human cells and people."